I'm trying to send mail via SQL DB Mail. I have the profile and account setup and working. When I send email to an internal recipient everything works fine. But if I try to send to an email address that is not internal, I get this error message:
Cannot send mails to mail server. (Mailbox unavailable. The server response was: 5.7.1 Unable to relay for firstname.lastname@example.org).
The server OS is Server 2003.
How can I fix this?